Workshop

program in a name entry; entering the correct number for a given name is important.
In particular, TCP/IP name services, although powerful and able to handle millions and millions of
names, isn’t exactly plug-and-play. The DNS (Domain Name Service) that you use when surfing the
Web works pretty automatically for you once it’s configured correctly, and it will translate
www.co.chatham.ga.us to 167.195.160.9. However, you’ll need to know the exact number of your DNS
server. Unlike telephone information, DNS servers all have different addresses; verifying that a
workstation’s DNS server is correct can be an important troubleshooting step (see Figure 1.5).
Figure 1.5 Name resolution on DNS.
Note that most smaller sites that use TCP/IP usually don’t have DNS set up. Instead, each workstation
has a local (hard drive) “hosts” file that lists the addresses and host names the workstation needs to get
to. (Think of this as your personal phone book rather than the corporate directory.) As you can imagine,
this gets hard to manage when you have more than a handful of workstations, unless the addresses of the
servers never change. As sites grow, or as they get connected to the Internet, DNS servers are added. Can
you imagine how big a single file with all the servers on the Internet would be? Fortunately, each DNS
server for a given DNS zone is only responsible for its own information.
A DNS zone (its scope of responsibility for naming) can be huge—for example, .com has millions of
subzones (yahoo.com, jotto.com, and so on); on the other hand, it can be small—for example,
feldman.org lists only one host (www.feldman.org) and no subzones.
With DNS servers getting easier to manage and being a mandatory component of Internet access, you
can expect to see more of them in smaller shops as time goes on. It’s worth mentioning that each DNS
server is responsible for only its own zone, so if you can’t get to one particular address (say,
yahoo.com) but can get to another (say, jotto.com), it may be that the name server responsible for
that zone is down. On the Internet at large, this rarely happens, because the DNS organizers require backup
DNS servers for a zone. DNS problems are more likely to happen within a smaller organization’s
intranet, particularly when all the eggs for that organization are in one basket.
Remember that you can still dial a number yourself when your speed dial buttons are broken. Similarly, if
you cannot get to something on your network, try getting to it by number. For example, rather than going
to http://www.co.chatham.ga.us, you could try http://167.195.160.6. If this works, you know there’s
something up with name services.